Create rule S7050: Void functions should not return null (avoid_retur…

…ning_null_for_void)

Co-authored-by: antonioaversa <[email protected]>

rules/S7050/dart/metadata.json

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+{
+  "title": "Void functions should not return null",
+  "type": "CODE_SMELL",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "1min"
+  },
+  "tags": [
+  ],
+  "defaultSeverity": "Minor",
+  "ruleSpecification": "RSPEC-7050",
+  "sqKey": "S7050",
+  "scope": "All",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "MAINTAINABILITY": "LOW"
+    },
+    "attribute": "CLEAR"
+  }
+}

rules/S7050/dart/rule.adoc

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+Functions and methods with `void` return type should not return `null`.
+
+== Why is this an issue?
+
+Dart allows to `return null;` from a function or a method with `void` return type. That happens because, from a technical standpoint, unlike other languages like Java, every function in Dart returns a value: if you don't return a value, `null` will be returned.
+
+From a semantical standpoint, however, this can be misleading, as it may suggest that the function does return an intended value, which is not the case.
+
+It is better to consistently use `return;` and make it clear that in fact the function does not return any intended value.
+
+== How to fix it
+
+Replace `return null;` with `return;`.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,dart,diff-id=1,diff-type=noncompliant]
+----
+void logIf(bool condition, String message) {
+  if (!condition) {
+    return null; // Noncompliant
+  }
+
+  print(message);
+}
+----
+
+==== Compliant solution
+
+[source,dart,diff-id=1,diff-type=compliant]
+----
+void logIf(bool condition, String message) {
+  if (!condition) {
+    return;
+  }
+
+  print(message);
+}
+----
+
+== Resources
+
+=== Documentation
+
+* Dart Docs - https://dart.dev/tools/linter-rules/avoid_returning_null_for_void[Dart Linter rule - avoid_returning_null_for_void]
+
+
+ifdef::env-github,rspecator-view[]
+
+'''
+== Implementation Specification
+(visible only on this page)
+
+=== Message
+
+* Don't return 'null' from a function with a return type of 'void'.
+* Don't return 'null' from a method with a return type of 'void'.
+
+=== Highlighting
+
+* In the case of a function or method with body: the `return null;` expression, including `;`.
+* In the case of an arrow function or an arrow method: the `=> null;` expression, including `;`.
+
+
+'''
+== Comments And Links
+(visible only on this page)
+
+endif::env-github,rspecator-view[]

rules/S7050/metadata.json

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+{
+}